cocos_lib/cocos/primitive/Box.cpp

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#include "primitive/Box.h"
#include "base/std/optional.h"

namespace cc {
namespace {
const ccstd::vector<ccstd::vector<uint32_t>> FACE_AXES{
    {2, 3, 1}, // FRONT
    {4, 5, 7}, // BACK
    {7, 6, 2}, // TOP
    {1, 0, 4}, // BOTTOM
    {1, 4, 2}, // RIGHT
    {5, 0, 6}  // LEFT
};

const ccstd::vector<ccstd::vector<float>> FACE_NORMALS{
    {0, 0, 1},  // FRONT
    {0, 0, -1}, // BACK
    {0, 1, 0},  // TOP
    {0, -1, 0}, // BOTTOM
    {1, 0, 0},  // RIGHT
    {-1, 0, 0}  // LEFT
};

const ccstd::vector<ccstd::vector<float>> FACE_TANGENTS{
    {-1, 0, 0, 1}, // FRONT
    {-1, 0, 0, 1}, // BACK
    {-1, 0, 0, 1}, // TOP
    {-1, 0, 0, 1}, // BOTTOM
    {0, 0, -1, 1}, // RIGHT
    {0, 0, 1, 1}   // LEFT
};
} // namespace

IGeometry box(const ccstd::optional<IBoxOptions> &options) {
    const uint32_t ws = options->widthSegments.has_value() ? options->widthSegments.value() : 1;
    const uint32_t hs = options->heightSegments.has_value() ? options->heightSegments.value() : 1;
    const uint32_t ls = options->lengthSegments.has_value() ? options->lengthSegments.value() : 1;

    const float hw = options->width.has_value() ? options->width.value() / 2 : 1.0F / 2;
    const float hh = options->height.has_value() ? options->height.value() / 2 : 1.0F / 2;
    const float hl = options->length.has_value() ? options->length.value() / 2 : 1.0F / 2;

    ccstd::vector<Vec3> corners{Vec3{-hw, -hh, hl}, Vec3{hw, -hh, hl}, Vec3{hw, hh, hl}, Vec3{-hw, hh, hl}, Vec3{hw, -hh, -hl}, Vec3{-hw, -hh, -hl}, Vec3{-hw, hh, -hl}, Vec3{hw, hh, -hl}};

    ccstd::vector<float> positions;
    ccstd::vector<float> normals;
    ccstd::vector<float> uvs;
    ccstd::vector<float> tangents;
    ccstd::vector<uint32_t> indices;
    const Vec3 minPos(-hw, -hh, -hl);
    const Vec3 maxPos(hw, hh, hl);
    float boundingRadius{static_cast<float>(sqrt(hw * hw + hh * hh + hl * hl))};

    auto buildPlane = [&](uint32_t side, uint32_t uSegments, uint32_t vSegments) {
        float u = 0;
        float v = 0;
        const auto offset = static_cast<uint32_t>(positions.size() / 3);
        const ccstd::vector<uint32_t> faceAxe = FACE_AXES[side];
        const ccstd::vector<float> faceNormal = FACE_NORMALS[side];
        const ccstd::vector<float> faceTangent = FACE_TANGENTS[side];

        for (index_t iy = 0; iy <= vSegments; ++iy) {
            for (index_t ix = 0; ix <= uSegments; ++ix) {
                u = static_cast<float>(ix) / static_cast<float>(uSegments);
                v = static_cast<float>(iy) / static_cast<float>(vSegments);
                Vec3 temp1 = corners[faceAxe[0]].lerp(corners[faceAxe[1]], u);
                Vec3 temp2 = corners[faceAxe[0]].lerp(corners[faceAxe[2]], v);
                temp2.subtract(corners[faceAxe[0]]);
                temp1.add(temp2);
                positions.emplace_back(temp1.x);
                positions.emplace_back(temp1.y);
                positions.emplace_back(temp1.z);

                normals.emplace_back(faceNormal[0]);
                normals.emplace_back(faceNormal[1]);
                normals.emplace_back(faceNormal[2]);

                uvs.emplace_back(u);
                uvs.emplace_back(v);
                tangents.emplace_back(faceTangent[0]);
                tangents.emplace_back(faceTangent[1]);
                tangents.emplace_back(faceTangent[2]);
                tangents.emplace_back(faceTangent[3]);

                if ((ix < uSegments) && (iy < vSegments)) {
                    auto uSeg1 = uSegments + 1;
                    const auto a = ix + iy * uSeg1;
                    const auto b = ix + (iy + 1) * uSeg1;
                    const auto c = (ix + 1) + (iy + 1) * uSeg1;
                    const auto d = (ix + 1) + iy * uSeg1;

                    indices.emplace_back(offset + a);
                    indices.emplace_back(offset + d);
                    indices.emplace_back(offset + b);

                    indices.emplace_back(offset + b);
                    indices.emplace_back(offset + d);
                    indices.emplace_back(offset + c);
                }
            }
        }
    };

    buildPlane(0, ws, hs); // FRONT
    buildPlane(4, ls, hs); // RIGHT
    buildPlane(1, ws, hs); // BACK
    buildPlane(5, ls, hs); // LEFT
    buildPlane(3, ws, ls); // BOTTOM
    buildPlane(2, ws, ls); // TOP

    IGeometry info;
    info.positions = positions;
    info.normals = normals;
    info.uvs = uvs;
    info.tangents = tangents;
    info.boundingRadius = boundingRadius;
    info.minPos = minPos;
    info.maxPos = maxPos;
    info.indices = indices;
    return info;
}

} // namespace cc